Question

Find the sum of first 20 terms of an AP series 5+10+15.......... using suitable
formula​

Answer 1

Answer:

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Answer 2

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→ ${s}_{n}=\frac{n}{2} \times ( 2a + ( n - 1 ) d )$

→ ${s}_{n} = \frac{20}{2} \times ( 2(5) +(19)5)$

→ ${s}_{n} = 10 \times ( 10 + 95)$

→ ${s}_{n} = 1050$